I am sure this had been said before, obviously, about why the Fog World exists and what it is for. (Not only that it exists in Silent Hill, but in general ) I think that it exists because it is the lubrication.

Which is? Transition! Transition. Water made it easier to shift worlds. The Fog World would help one transition, lube them up for travel, literally and figuratively ( one can be readied in many ways) . It is there as the last level of protection from the elements of the real world and the otherworld. The world between worlds.

It moves, it crawls, it drapes but it ALWAYS moves

What is fog?

Fog is a collection of water droplets or ice crystals suspended in the air at or near the Earth’s surface. While fog is a type of a cloud, the term “fog” is typically distinguished from the more generic term “cloud” in that fog is low-lying, and the moisture in the fog is often generated locally (such as from a nearby body of water, like a lake or the ocean, or from nearby moist ground or marshes).Fog is distinguished from mist only by its density, as expressed in the resulting decrease in visibility: Fog reduces visibility to less than 1 km (5/8 statute mile), whereas mist reduces visibility to no less than 1 km (5/8 statute mile). For aviation purposes in the UK, a visibility of less than 2 km but greater than 999 m is considered to be mist if the relative humidity is 95% or greater – below 95% haze is reported.

What is the symbolism of Fog?

It covers up reality… or so we think.

Psychological Meaning: You are not seeing things as they really are. You may be disorientated in waking life and have lost your sense of direction. It is time to finish with this foggy thinking. Be clear about what you want and what direction you want your life to take. Deliberate decisiveness will improve your inner clarity.

Mystical Meaning: If the fog is thick, this is a very bad omen say the dream oracles, but if you dream of it clearing you will have great success.

fog distorts and can be used to hide in. it’s also a symbol of how black and white can be blurred to a foggy grey, life is not as simple as it seems, especially in the darkness.

represents a sense of being lost and confused. Of not knowing where you are going. Fog can also symbolize the realm of the unconscious, which you may be exploring or attempting to navigate

So we can easily say fog is water in a different form.

Now, let us look at the different symbolism of water.

purity and fertility – source of life
symbolism of circulation, life, cohesion and birth by associating the creative waters of the earth with the fluids found in our own body (i.e., blood, our own water).
water is the epitome symbol for metamorphosis and philosophical recycling. everything comes from water and returns to it.

Transformation

Subconscious

Fertilization

Purification

Reflection

Intuition

Renewal

Blessing

Motion

Life

( I had to add this, stars are just that awesome)
Much of the universe’s water is produced as a byproduct of star formation. When stars are born, their birth is accompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts the surrounding gas, the shock waves that are created compress and heat the gas. The water observed is quickly produced in this warm dense gas On 22 July 2011, a report described the discovery of a gigantic cloud of water vapor, containing “140 trillion times more water than all of Earth’s oceans combined,” around a quasar located 12 billion light years from Earth. According to the researchers, the “discovery shows that water has been prevalent in the universe for nearly its entire existence.”
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Now, what does lubrication mean?
the condition of having been made smooth or slippery by the application of a lubricant, to make transition easier.
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This “lube” Fog World may not appear many times and one would find themselves easily in the Otherworld, easily skipping the world between worlds. However, one
would only need small contact with WATER any form of it, for the gears to start rolling. And some parts of the Otherworld are one’s own reflection and that of others, water is key in reflections. The fog world is that protective membrane, giving someone a chance to stop and reflect after they’ve tired themselves from the endless wandering ( NOT SAYING IT IS THE SAFETY OF ALL SAFETY- there are dangers in fog no fooling) Fog World just makes one ready to easily land in another type of hell.